1. Field
The present invention relates to a multi-directional projection type moire interferometer and an inspection method of using the same, and more particularly, to a multi-directional projection type moire interferometer capable of multi-directionally emitting the pattern illumination toward a target object to eliminate a complex shadow area of the target object according to various shapes thereof, and an inspection method of using the same.
2. Background
Hereinafter, a conventional projection type moire interferometer will be described with reference to FIG. 1. As shown in FIG. 1, the conventional moire interferometer includes a plurality of projectors 3 generating a bi-directional pattern illumination and one image formation part 4.
The plurality of projectors 3 is provided to be inclined on one side and another side of the image formation part 3, respectively. The projector 3 includes an illumination part 3a, a grating element 3e, a grating actuator 3f, and an emitting lens 3g to generate the pattern illumination. The illumination part 3a includes an illumination source 3b and a plurality of emitting lenses 3c and 3d. After the illumination that is generated from the illumination source 3b of the illumination part 3a passes through the plurality of emitting lenses 3c and 3d, the pattern illumination is formed via grating patterns formed on the grating element 3e. The pattern illumination according to the grating patterns passes through the emitting lens 3g and is bi-directionally emitted toward a target object 1 placed on an XY table 2. The XY table 2 is actuated by a table actuator 2a to move the target object into either X or Y direction.
The image formation part 4 includes a charge-coupled device (CCD) camera 4a, an imaging lens 4b, and a filter 4c. The image formation part 4 takes a pattern image according to the pattern illumination reflected from the target object 1. Also, a circular lamp 5 is provided below the image formation part 4. The circular lamp 5 is used as an illumination source when taking a particular shape of the target object 1. When an N-bucket algorithm is applied to inspect a 3 dimensional (3D) shape of the target object 1 in a state where the target object 1 is placed on the XY table 2, the image formation part 4 takes N images while moving the grating element 3e via the grating actuator 3f N times. When the N images are taken and obtained, a control unit (not shown) obtains phase information using the obtained images. Also, when the plurality of projectors 3 obtains each phase information, the control unit calculates an integrated phase map in which noise is removed, and inspects a height-map and a 3D shape of the target object 1 using the calculated integrated phase map.
The conventional projection type moire interferometer emits an illumination toward a target object and inspects the target object in a state where a plurality of projectors is provided to face each other based on the target object. In this case, if the target object has a very complex shape, a shadow region may be incompletely removed, which results in inaccurately inspecting the target object.